A5074118258- 2D Materials and Applications
- Molecular Junctions and Nanostructures
- Physics of Superconductivity and Magnetism
- Chalcogenide Semiconductor Thin Films
- Topological Materials and Phenomena
- Electronic and Structural Properties of Oxides
- Advanced Condensed Matter Physics
- Organic and Molecular Conductors Research
- Machine Learning in Materials Science
- Iron-based superconductors research
- Graphene research and applications
- Advanced Thermoelectric Materials and Devices
- Inorganic Chemistry and Materials
- Superconductivity in MgB2 and Alloys
- Advanced Chemical Physics Studies
- Perovskite Materials and Applications
- Quantum and electron transport phenomena
- MXene and MAX Phase Materials
- Rare-earth and actinide compounds
- Ga2O3 and related materials
- Magnetic and transport properties of perovskites and related materials
University of Fribourg
2019-2024
School of Engineering and Architecture of Fribourg
2023
Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties still infancy. In particular, the diverse phase transitions topological states two-dimensional (2D) transition metal dichalcogenides (TMDs) remains an open challenge. Here, we exploit uniaxial stabilize long-debated structural ground state of 2D semimetal IrTe$_2$, which hidden unstrained samples....
Interlayer coupling is strongly implicated in the complex electronic properties of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>1</a:mn><a:mi>T</a:mi></a:mrow><a:mo>−</a:mo><a:msub><a:mi>TaS</a:mi><a:mn>2</a:mn></a:msub></a:math>. Uniaxial strain engineering offers a route to modify this order elucidate its interplay with structure and correlations. Here, we employ angle-resolved photoemission spectroscopy (ARPES) reveal effect uniaxial on <b:math...
The transition-metal dichalcogenide $1T\ensuremath{-}{\mathrm{TiSe}}_{2}$ is a quasi-two-dimensional layered material with phase transition towards commensurate charge-density wave (CDW) at critical temperature ${T}_{c}\ensuremath{\approx}200\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. relationship between the origin of CDW instability and semimetallic or semiconducting character normal state, i.e., nonreconstructed Fermi-surface topology, remains elusive. By combining angle-resolved...
Spatially inhomogeneous electronic states are expected to be key ingredients for the emergence of superconducting phases in quantum materials hosting charge-density-waves (CDWs). Prototypical transition-metal dichalcogenides (TMDCs) and among them, 1$T$-TiSe$_2$ exhibiting intertwined CDW under Cu intercalation, pressure or electrical gating. Although it has been recently proposed that superconductivity relates fluctuations development spatial inhomogeneities order, fundamental mechanism...
$\alpha$-GeTe(111) is a non-centrosymmetric ferroelectric material, for which strong spin-orbit interaction gives rise to giant Rashba split states in the bulk and at surface. The detailed dispersions of surface inside band gap remains an open question because they are located unoccupied part electronic structure, making them inaccessible static angle-resolved photoemission spectroscopy. We show that this difficulty can be overcome via in-situ potassium doping surface, leading rigid shift 80...
In the transition metal dichalcogenide ${\mathrm{IrTe}}_{2}$, low-temperature charge-ordered phase transitions involving Ir dimers lead to occurrence of stripe phases different periodicities, and nearly degenerate energies. Bulk-sensitive measurements have shown that, upon cooling, ${\mathrm{IrTe}}_{2}$ undergoes two such first-order $(5\ifmmode\times\else\texttimes\fi{}1\ifmmode\times\else\texttimes\fi{}5)$ $(8\ifmmode\times\else\texttimes\fi{}1\ifmmode\times\else\texttimes\fi{}8)$...
Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schr\"odinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of $1T\text{\ensuremath{-}}{\mathrm{TiSe}}_{2}$ induce creation a two-dimensional electron gas (2DEG) quantum confinement its charge-density wave (CDW) at surface. By further changing K coverage, tune carrier density within 2DEG allows us to nullify, surface, electronic...
Abstract Investigations of magnetically ordered phases on the femtosecond timescale have provided significant insights into influence charge and lattice degrees freedom magnetic sub-system. However, short-range correlations occurring in absence long-range order, for example spin-frustrated systems, are inaccessible to many ultrafast techniques. Here, we show how time-resolved resonant inelastic X-ray scattering (trRIXS) is capable probing such short-ranged dynamics a charge-transfer...
Black phosphorus is a quasi-two-dimensional layered semiconductor with narrow direct band gap of 0.3 eV. A giant surface Stark effect can be produced by the potassium doping black phosphorus, leading to semimetal phase transition originating from creation strong dipole and associated bending. By using time- angle-resolved photoemission spectroscopy, we report partial photoinduced screening this bending compensating photovoltage. We further resolve detailed dynamics at pertinent timescales...
Abstract The interplay of nearly degenerate orders in quantum materials can lead to a myriad emergent phases. A prominent case is that the high- T c cuprates for which relationship between superconductivity and short-ranged, incommensurate charge density wave CuO 2 planes involving $$d_{x^2 - y^2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:msup> <mml:mi>x</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>−</mml:mo>...
Abstract Electron-phonon coupling, i.e., the scattering of lattice vibrations by electrons and vice versa, is ubiquitous in solids can lead to emergent ground states such as superconductivity charge-density wave order. A broad spectral phonon line shape often interpreted a marker strong electron-phonon coupling associated with Fermi surface nesting, parallel sections connected momentum. Alternatively phonons are known arise from atomic anharmonicity. Here, we show that broadening occur...
Interlayer coupling is strongly implicated in the complex electronic properties of 1$T$-TaS$_2$ , but interplay between this and correlations remains unresolved. Here, we employ angle-resolved photoemission spectroscopy (ARPES) to reveal effect uniaxial strain engineering on structure interlayer . The normally insulating ground state transformed into a correlated-metal phase under strain, as evidenced by emergence narrow band at Fermi level. Temperature dependent ARPES measurements that...
The semimetallic or semiconducting nature of the transition metal dichalcogenide 1$T$-TiSe$_2$ remains under debate after many decades mainly due to fluctuating its 2 $\times$ charge-density-wave (CDW) phase at room-temperature. In this letter, using angle-resolved photoemission spectroscopy, we unambiguously demonstrate that normal state is with an electron-hole band overlap $\sim$110 meV by probing low-energy electronic states perturbed CDW strongly doped alkali atoms. Our study not only...
Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schrödinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of 1$T$-TiSe$_2$ induce creation a two-dimensional electron gas (2DEG) quantum confinement its charge-density-wave (CDW) at surface. By further changing K coverage, tune carrier-density within 2DEG allows us to nullify, surface, electronic energy gain due exciton condensation...
Competing interactions in low-dimensional materials can produce nearly degenerate electronic and structural phases. We investigate phase transitions layered <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>IrTe</a:mi><a:mn>2</a:mn></a:msub></a:math> for which a number of potential transition mechanisms have been postulated. The spatial coexistence multiple phases on the micron scale has prevented detailed analysis structure. By exploiting micro-angle-resolved photoemission...
A Correction to this paper has been published: https://doi.org/10.1038/s41535-021-00323-8
We present a combined angle-resolved photoemission spectroscopy and low-energy electron diffraction (LEED) study of the prominent transition metal dichalcogenide IrTe$_2$ upon potassium (K) deposition on its surface. Pristine undergoes series charge-ordered phase transitions below room temperature that are characterized by formation stripes Ir dimers different periodicities. Supported density functional theory calculations, we first show K atoms dope topmost layer with electrons, therefore...
IrTe2undergoes a series of charge-ordered phase transitions below room temperature that are characterized by the formation stripes Ir dimers different periodicities. Full hemispherical x-ray photoelectron diffraction (XPD) experiments have been performed to investigate atomic position changes undergone near surface 1T-IrTe2in first-order transition, from (1 × 1) (5 phase. Comparison between experiment and simulation allows us identify consequence dimerization on atoms local environment. We...